Managed metadata is very powerful but still limited tool, like:

1. SharePoint REST api still does not fully support MMS columns;
2. Using taxonomy fields in CSOM or PowerShell are also not straightforward as it looks like.
3. You can face some issues in external analytical tools like Power I.
4. It is difficult for users to handle the data for end users.
5. It is limited capabilities to view and manage custom properties of the taxonomy tags. Users will not be able to view address data in the columns as they could using dependant lookups

Your proposed solution is technically possible, but you have to check these points:

1. Who will manage the customer data? End users or system administrators? How many customers entries will it be? How often the data will change?
2. Your approach to have custom property in the term and copy the data to the item is possible. But think how will you handle when you have to depersonalize information according to GDPR requirements (if applicable)
3. What is later you will need more data related to customer

Taxonomy is absolutely suitable for stable enterprise wide dimensions or hierarchies. On the other hand, customers data often grow and change.

Take some time to think about similar solution:

1. create a dedicated site for central customer data. Call it something like /sites/CRM
2. Create a list for for customer data. Add as many columns as you need for this list, like address, bank account, etc. This list will be central repository for customer data. It will be user friendly and user will be able to handle the data themselves.
3. Create the same list in all other sites where you will need customer data. It is easy to create a list based on another list using modern ui.
4. Use Power Automate (or remote event receiver) to copy the data from central CRM site to all other sites on every change. The flow could use trigger that would fire on every change of the central CRM list. The flow should create or update customer data entries in all other sites.

In this scenario you can use all customer data in all your sites using lookups and dependant lookups. This solution will also help you to comply with GDPR requirements.

Managed metadata is very powerful but still limited tool, due to:

1. SharePoint REST api still does not fully support MMS columns;
2. Using taxonomy fields in CSOM or PowerShell are also not straightforward as it looks like.
3. You can face some issues in external analytical tools like Power BI.
4. It is difficult for users to handle the taxonomy data.
5. It is limited capabilities to view and manage custom properties of the taxonomy tags. Users will not be able to view address data in the columns as they could using dependant lookups

Your proposed solution is technically possible, but you have to check these points:

1. Who will manage the customer data? End users or system administrators? How many customers entries will it be? How often the data will change?
2. What if later you will need to have more data related to the customer
3. Your approach to have custom property in the term and copy the data to the item is possible. But think how will you handle when you have to depersonalize information according to GDPR requirements (if applicable)

Taxonomy is absolutely suitable for stable enterprise wide dimensions or hierarchies. On the other hand, customers data often grow and change.

Take some time to think about similar solution:

1. create a dedicated site for central customer data. Call it something like /sites/CRM
2. Create a list for for customer data. Add as many columns as you need for this list, like address, bank account, etc. This list will be central repository for customer data. It will be user friendly and user will be able to handle the data themselves.
3. Create the same list in all other sites where you will need customer data. It is easy to create a list based on another list using modern ui.
4. Use Power Automate (or remote event receiver) to copy the data from central CRM site to all other sites on every change. The flow could use trigger that would fire on every change of the central CRM list. The flow should create or update customer data entries in all other sites.

In this scenario you can use all customer data in all your sites using lookups and dependant lookups. This solution will also help you to comply with GDPR requirements.